Supporting structure for the blades of turbomachines

ABSTRACT

In and for a fluid handling turbomachine having a relatively rotatable bladed stator and rotor, a blade supporting structure comprising at least one corrugated annular element coaxial with the axis of the machine and perforated with openings in each of which a blade is fitted or embedded at one of its ends in order that the blade body is disposed obliquely in relation to the general direction of the corrugations in said corrugated element.

United States Patent Bruneau et al. 1 1 Jan. 2, 1973 54 SUPPORTING STRUT FOR HE 3,303,998 2/1967 146a et a1 ..41s/21s 2,724,546 11/1955Barrett, Jr. et a1. ..4l5/|93 [75] Inventors: Henri Bruneau,LHay-les-Roses; FOREIGN PATENTS OR APPUCATlONS Gerhard e Dammarie-les-154,605 1/1954 Canada ..415/217 Lys; Marcel Joseph Tournere, Paris,1,028,444 5/1966 Great Britain ..415/53 all Of France 994,568 6/1965Great Britain ..415/190 [73] Assignee: Societe Nationale DEtude et deCon- Primary Examiner Hemy F. Raduazo struction de Moteurs D'Avlatlon,mmmey-wi|liam Danie] Paris, France 1221 Filed: Nov. 30, 1970 1571ABSTRACT In and for a fluid handlin turbomachine havin a 21 A 1. .1 5 gg 1 pp No 93 65 relat1vcly rotatable bladed stator and rotor, a bladesupporting structure comprising at least one corru- [30] ForeignApplication Priorit Data gated annular element coaxial with the axis ofthe machine and perforated with openings in each of France "694mm whicha blade is fitted or embedded at one of its ends in order that the bladebody is disposed obliquely in .415/217, 9. 415/214 relation to thegeneral direction of the corrugations in [5 1 Int. Cl. .,F04d 29/40,F04d 19/02 said corrugated element. [58] Field of Search ..415/53. 190,191, 193, 216, 415/217, 218, 219, 172, 214

[56] References Cited 16 Claims, 17 Drawlng Figures UNITED STATESPATENTS 3,291,382 12/1966 Blackhurst et a1 415 214 PATENTEDJAN 2197sSHEU 3 [IF 4 PATBHED II 2W 3,708,242

saw u or 4 rIIIIIIIII/I SUPPORTING STRUCTURE FOR THE BLADES FTURBOMACHINES This invention relates to a supporting structure forblades, for example, stator blades, in a fluid handling machine having arelatively rotatable stator and rotor, hereinafter referred to as aturbomachine, such as a compressor, a turbine or a pump.

A structure of this kind is often designed to withstand the keystresses, in particular bending, to which the machine is subjected andmust, consequently, have a high stiffness.

Known structures employed for this purpose generally comprise anexternal structure made up, for example, of a set of cylindrical orfrusto-conical casings assembled together axially, or again twohalf-shells joined to one another along an axial plane. The statorblades are fixed, at one of their ends, to said external structure, inorder to form one or more successive blade rows. It is oftenadvantageous, where the attainment of rigidity in the assembly isconcerned, to make this a rigid attachment, for example by effecting thesame by brazing or welding, so that it consequently represents anembedded or restrained attachment. Equally, it is possible to provide aninternal structure to which the blades are fixed by their other ends.

Because of their stiffness, the supporting structures thus far knownexhibit the drawback, in particular in the case where the blades arefixed to them in embedded fashion, that they do not provide adequatedamping of the vibrations to which the blades are subjected in operationand this makes for increased risk of fatigue failure on the part of theblades. These structures are, furthermore, relatively heavy and this isa particular drawback where the turbomachine is designed for part of agas-turbine power plant for aviation applications.

The object of the invention is simultaneously to overcome these twodrawbacks.

In accordance with the invention, therefore, a bladesupporting structureis designed to comprise at least one corrugated or undulating annularelement disposed coaxially relative to the axis of the machine, saidelement being formed with openings in which each of the blades is fittedat one of its ends, each of said openings extending in a directionoblique to the general directions of the folds or corrugations in saidcorrugated element and passing through at least two successivecorrugations. Preferably, said corrugated element will be locatedbetween two skins or liners, so as to form the core of a sandwichstructure.

This structure, in the application with which the invention isconcerned, has the essential advantage of combining two apparentlycontradictory qualities, namely a high structural rigidity, thusenabling the supporting structure which it forms to withstand at leastsome of the main stresses to which the machine is subjected, and, on theother hand, a local flexibility which makes it possible to damp thevibrations developing in the blades which are fixed to said structure.This structure is, furthermore, much lighter than the conventionalsupporting structures whilst having the same or even better stiffness.

The corrugated element doing duty as the core of the structure can beassembled so that the general direction of its folds or corrugations issubstantially parallel to the axis of the turbomachine, this, inparticular, making for high transverse stiffness. Equally, how ever, itcan be assembled in such a manner, and in particular in the case wherethe supporting structure does not have to withstand any substantialbending stresses, that the general direction of its folds orcorrugations is substantially circumferential.

In accordance with one advantageous embodiment, the core of the sandwichstructure may comprise at least two generally concentric corrugatedelements, whose folds or corrugations extend either in the samedirection (advantageously with different or with a certain difference inphase), or in two mutually perpendicular directions. In this manner,simultaneously both the stiffness of the supporting structure and itscapacity to damp blade vibrations, are improved.

In accordance with another arrangement of the invention, applicable inparticular to situations where considerations of weight are ofrelatively minor importance, the supporting sandwich structure can befixed to the interior of a conventional rigid external housing casing.

The description which now follows in relation to the accompanyingdrawing will indicate how the invention may be carried into practice.

IN THE DRAWINGS:

FIG. 1 is a schematic view, in section on an axial plane, of a part ofthe stator of a turbomachine comprising a stator blade supportingstructure in accordance with the invention;

FIGS. 2 to 11 are schematic views relating to different embodiments ofsaid supporting structure or to its assembly;

FIGS. la, 2a and 5a are sectional views on the lines Ia-la, Ila-Ila andVa-Va respectively, of the structures respectively illustrated in FIGS.1,2 and 5;

FIGS. l2, l3 and 14 are explanatory diagrams relating to the vibratoryphenomena occurring in the turbomachine during operation.

In FIGS. 1 and la, part of the stator of a turbomachine, such as anaxial-flow compressor for a turbojet engine, has been shown, and indeed,more specifically, a supporting structure for a row of stator blades 1.This structure comprises an external casing section 2 and a internalcasing section 3 each constituted, in part at least, by a body ofsandwich structure. Each of these sections comprises an annularcorrugated element 2a or 30 forming the core, between two skins" 3b, 3cor 3!), Be. In this example, the general direction of the folds orcorrugations in the elements 2a and 3a is substantially circumferential.

In order to enable an external casing section 2 to be assembled to thenext adjacent casing (not shown), there is fixed to each end of thecasing section, for example by welding and after previous local pinchingof the sandwich structure, a ring 4 formed with a groove 4a or with atongue so that sealed attachment to an adjacent complementary ring,belonging to the next casing section, can be effected.

The sandwich structure of the internal casings 3 is likewise pinched atits edges and bent in order to enable the attachment, for example bywelding or brazing, of sealing rings 5. These latter operate in a mannerknown per se with labyrinth arrangements carried by the rotor of themachine and shown in FIG. 11.

The external casing section 2 and the internal casing section 3 arepunched to fit the shape and setting angle of the blades 1. Thus,elongated openings are formed each of which extends lengthwise in adirection oblique to the general direction of the corrugations in thecorrugated elements 20 and 3a and passes through or across at least twosuccessive corrugations. In these elongated openings the respective endsof the blades are fitted either by simply press-fitting them inposition, or by securing them by some other method such as welding,brazing, diffusion or bonding. H05. 2 and 2a relate to a variantembodiment in accordance with which the general direction of the foldsor corrugations in the corrugated elements 20, 3a, is substantiallyparallel to the axis of the turbomachine. In addition, the rings 4 ofFIG. 1 are replaced by flanges 6 attached, for example by welding, tothe two previously pinched ends of the casing section 2. The adjacentflanges of two successive casing sections are advantageously assembledtogether by bolts.

FIG. 3 relates to a variant embodiment in accordance with which theexternal supporting structure comprises a plurality of easing sections2, cylindrical or frusto-conical in form, assembled together axially. Atleast at one of its ends, the structure terminates in an attached flange7 similar (with the exception of a shoulder 70 to the flanges 6described in respect of FIG. 2. The fixing together of the casingsections 2, on the other hand, is effected by flanges 8 which areproduced by pinching and folding the sandwich structure itself, saidflanges being bolted together at 9.

FIG. 4 illustrates a variant embodiment which differs from thearrangement shown in FIG. 1 simply by the fact that the tongued andgrooved rings 4 are replaced by rings 10 with interlocking teeth 11 sothat the casing sections are centered and prevented from rotating inrelation to one another.

FIGS. 5 and 5a relate to a variant embodiment of the arrangement shownin FIGS. 2 and 2a, in accordance with which the folds or corrugations inthe corrugated elements 2a and 3a extend respectively in circumferentialand axial directions. FIG. 5 likewise illustrates the fixing together ofthe successive flanges, by bolts 12.

FIGS. 6 and 7 relate to variant embodiments of the invention in whichthe core of the sandwich structure is made up of at least two concentriccorrugated annular elements 120, 22a, separated from one another by anintermediate skin" 2d. In accordance with the embodiment shown in FIG.6, the folds or corrugations in said elements extend in two mutuallyperpendicular directions, namely circumferentially in the case of theelement 12a and axially in the case of the element 22a. In theembodiment shown in FIG. 7, these folds extend in the same direction,for example circumferentially. In this case, the spacing or the phase ofthe corrugations 120 will advantageously be made different to that ofthe corrugations 220, this increasing the transverse rigidity of thesupporting structure assembly.

FIG. 8 illustrates a variant embodiment of the invention in accordancewith which the core of the sandwich structure comprises three concentriccorrugated annular elements 102a 112a, 122a, separated from one anotherby intermediate skins 2e, 2f. As in the case of FIG. 7, the spacing ofthe corrugations 112a differs from that of those 102a and 122a, andthese latter can themselves be so arranged in relation to one another asto give a certain difference in phase which is beneficial in increasingthe stiffness of the supporting structure assembly.

FIG. 9 relates to a variant embodiment of the invention in accordancewith which the corrugations of the element 2a, instead of being simpleas in the preceding cases, have a complex periodic profile.

FIGS. 10 and I1 relate to two variant embodiments of the invention inaccordance with which the supporting structures 2 (sandwich structures),for the stator blades, are fixed to the interior of a conventional rigidhousing constituted, for example, by a stack of rings such as thosemarked 20.

In accordance with FIG. 10, the supporting structures 2 present flanges21, 22 fixed by bolts 23 to the housing rings 20.

In accordance with FIG. 11, the supporting structures 2 are fixed to thehousing on the one hand in the circumferential direction by a system ofsplines 24, and on the other hand, in the axial direction, by the axialstacking of said structures and the fitting of retainer rings 25. Thisfigure also shows the relative arrangement of two rows of stator blades1 and a row of rotor blades 26 carried by a disc 27. Assembled on thelatter there are labyrinth arrangements 28 cooperating with the sealingrings 5.

FIGS. l2, l3 and 14 provide a highly schematic illustration of thevibratory phenomena to which reference has been made hereinbefore.

As those skilled in the art will realize, the stator blades 1, exposedto vibrations of aerodynamic nature in the fluid flowing through theturbomachine, themselves experience mechanical vibrations for example inthe fundamental mode 1a or at a harmonic, for example the secondharmonic lb. The amplitudes of these vibrations, illustrated in FIG. 12,have been exaggerated simply in order to clarify the drawing. As FIGS.13 and 14 show, the elongations e are along the large axis B-B of theblade profile.

The blades 1 are embedded at their respective ends in the supportingstructures 2, 3, namely the sandwich structures described hereinbefore.FIG. I3 corresponds to the case in which the corrugations in thematerial are axially disposed; this material then has a high radialrigidity and, by contrast, a certain degree of circumferentialflexibility. FIG. 14 relates to the case in which the corrugations inthe material extend circumferentially; its rigidity and flexibility arethen respectively circumferential and axial. In both cases and by virtueof the substantially oblique disposition of the blades I in relation tothe axis of the turbomachine, there is at least one component x or y, ofthe vibratory movement, in respect of which the restrained end of theblade cooperates with an elastic structure constituted by corrugatedelement 2a. Glven appropriate dimensioning and assembly of said element,it can be arranged that its resonance frequency is at all times farbelow that of the blade with the result that, as those skilled in theart will appreciate, the vibrations of the latter damped.

In the case where the sandwich structure utilized has two mutuallyperpendicular corrugation directions as shown for example in FIG. 6, oragain in the case where the directions of the corrugations in externaland internal supporting structures 2 and 3 respectively, are atright-angles to one another (as shown for example in H0. 5), thevibration-damping effect just referred to is still more pronounced.

The main stresses to which the turbomachine is subjected being generallyaxial and radial, it may be a useful feature to use for the externalsupporting structure a sandwich material incorporating at least oneelement with axial corrugations, as shown in FIGS. 2 and 6, at any ratein the case where it is necessary to take into account the internalarrangement of the corrugations in order to achieve a stiff statorassembly. On the other hand, where said stiffness is provided anyway bya conventional external casing, as shown in FIGS. and 11, the choice ofthe type of corrugations depends essentially upon its anti-vibrationproperties.

it will be apparent that the embodiments described are open tomodification in various ways without departing from the scope of theinvention as defined in the appended claims. Thus, in particular, thestator blades supporting structures which have been illustrated in theform of casing sections designed for axial assembly, could be replacedby half-shells or shell segments assembled together along axial lines.

We claim:

1. A turbomachine comprising at least one corrugated annular supportelement which extends coaxially with the axis of the machine, saidcorrugated element being perforated with a plurality of elongatedopenings each of which extends lengthwise in a direction oblique to thegeneral direction of the corrugations in said corrugated element andpasses through at least two successive corrugations, and a plurality ofblades each having one of its ends shaped to and fixedly fitted in acorresponding elongated opening and secured to a plurality of saidcorrugations.

2. A turbomachine according to claim 1 wherein the general direction ofthe corrugations in the corrugated element is substantially parallel tothe axis of the machine.

3. A turbomachine according to claim 1 wherein the general direction ofthe corrugations in the corrugated element is substantiallycircumferential.

4. A turbomachine according to claim 1 further com prising two skinsbetween which said corrugated element is located, whereby to form asandwich structure.

5. A turbomachine according to claim I comprising two corrugated annularelements arranged in radially spaced concentric coaxial relation to theaxis of the machine, each such element being perforated with a pluralityof elongated openings, each opening in a corrugated element extendinglengthwise in a direction oblique to the general direction of thecorrugations in said corrugated element and passing through at least twocorrugations in said element, each opening in one of said corrugatedelements being in radial registration with an opening in the othercorrugated element; and a plurality of blades each having its oppositeends fitting in a corresponding pair of radially spaced registeringopenings.

6. A turbomachine according to claim 5 wherein the corrugations in thetwo concentric corrugated elements extend in t e same, eneral d'rection.

7. A tur omachi e accor mg to claim 6 wherein the peaks of saidcorrugations in each of said elements are generally uniformly spacedapart and the spacing of the corrugations of the two elements isdifferent.

8. A turbomachine according to claim 6 wherein the corrugations in thetwo respective corrugated elements are each generally of the shape of aregular sinuous curve and the curves of the two elements are out ofphase.

9. A turbomachine according to claim 5 wherein the corrections in thetwo corrugated elements respectively extend at right angles to oneanother.

10. A turbomachine according to claim I wherein said annular corrugatedelement comprises at least two annular sections arranged in axialsucceeding relation.

11. A turbomachine according to claim 1 further comprising a rigidexternal housing, and means fixing said annular corrugated element tothe interior of said external housing.

12. A turbomachine according to claim 1 comprising at least twocorrugated annular elements arranged in radially adjacent concentriccoaxial relation to the axis of the machine, each such element beingperforated with a plurality of elongated openings, each opening in acorrugated element extending lengthwise in a direction oblique to thegeneral direction of the corrugations in said corrugated element andpassing through at least two corrugations in said element, each openingin one of said corrugated elements being in radial registration with anopening in at least one other corrugated element; and a plurality ofblades each having one of its ends fitting into at least twocorresponding registering openings in such radially adjacent corrugatedelements.

13. A turbomachine according to claim 12 wherein the corrugations in thetwo concentric corrugated elements extend in the same general direction.

14. A turbomachine according to claim 13 wherein the peaks of saidcorrugations in each of said elements are generally uniformly spacedapart and the spacing of the corrugations in the two elements isdifferent.

15. A turbomachine according to claim 13 wherein the corrugations in thetwo respective corrugated elements are each generally of the shape of aregular sinuous curve and the curves of the two elements are out ofphase.

16. A turbomachine according to claim 12 wherein the corrugations in thetwo corrugated elements respectively extend at right angles to oneanother.

1. A turbomachine comprising at least one corrugated annular supportelement which extends coaxially with the axis of the machine, saidcorrugated element being perforated with a plurality of elongatedopenings each of which extends lengthwise in a direction oblique to thegeneral direction of the corrugations in said corrugated element andpasses through at least two successive corrugations, and a plurality ofblades each having one of its ends shaped to and fixedly fitted in acorresponding elongated opening and secured to a plurality of saidcorrugations.
 2. A turbomachine according to claim 1 wherein the generaldirection of the corrugations in the corrugated element is substantiallyparallel to the axis of the machine.
 3. A turbomachine according toclaim 1 wherein the general direction of the corrugations in thecorrugated element is substantially circumferential.
 4. A turbomachineaccording to claim 1 further comprising two skins between which saidcorrugated element is located, whereby to form a sandwich structure. 5.A turbomachine according to claim 1 comprising two corrugated annularelements arranged in radially spaced concentric coaxial relation to theaxis of the machine, each such element being perforated with a pluralityof elongated openings, each opening in a corrugated element extendinglengthwise in a direction oblique to the general direction of thecorrugations in said corrugated element and passing through at least twocorrugations in said element, each opening in one of said corrugatedelements being in radial registration with an opening in the othercorrugated element; and a plurality of blades each having its oppositeends fitting in a corresponding pair of radially spaced registeringopenings.
 6. A turbomachine according to claim 5 wherein thecorrugations in the two concentric corrugated elements extend in thesame general direction.
 7. A turbomachine according to claim 6 whereinthe peaks of said corrugations in each of said elements are generallyuniformly spaced apart and the spacing of the corrugations of the twoelements is different.
 8. A turbomachine according to claim 6 whereinthe corrugations in the two respective corrugated elements are eachgenerally of the shape of a regular sinuous curve and the curves of thetwo elements are out of phase.
 9. A turbomachine according to claim 5wherein the corrections in the two corrugated elements respectivelyextend at right angles to one another.
 10. A turbomachine according toclaim 1 wherein said annular corrugated element comprises at least twoannular sections arranged in axial succeeding relation.
 11. Aturbomachine according to claim 1 further comprising a rigid externalhousing, and means fixing said annular corrugated element to theinterior of said external housing.
 12. A turbomachine according to claim1 comprising at least two corrugated annular elements arranged inradially adjacent concentric coaxial relation to the axis of themachine, each such element being perforated with a plurality ofelongated openings, each opening in a corrugated element extendinglengthwise in a direction oblique to the general direction of thecorrugations in said corrugated element and passing through at least twocorrugations in said element, each opening in one of said corrugatedelements being in radial registration with an opening in at least oneother corrugated element; and a plurality of blades each having one ofits ends fitting into at least two corresponding registering openings insuch radially adjacent corrugated elements.
 13. A turbomachine accordingto claim 12 wherein the corrugations in the two concentric corrugatedelements extend in the same general direction.
 14. A turbomachineaccording to claim 13 wherein the peaks of said corrugations in each ofsaid elements are generally uniformly spaced apart and the spacing ofthe corrugations in the two elements is different.
 15. A Turbomachineaccording to claim 13 wherein the corrugations in the two respectivecorrugated elements are each generally of the shape of a regular sinuouscurve and the curves of the two elements are out of phase.
 16. Aturbomachine according to claim 12 wherein the corrugations in the twocorrugated elements respectively extend at right angles to one another.